T-Belly Gen 4x

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T-Belly Gen 4x

Unread postby nomastomas » Thu Mar 12, 2015 4:36 am

The 4th generation T-Belly is now ready for surfing trials. Keep in mind that similar to the G2 and G3, the G4 is not a one-size-fits-all belly board. Rather, it is designed to “fit” the rider based upon rider height and weight. This G4 was built for me (5-10/190) The TBG4 is similar to its predecessor, the TBG3, with these exceptions: (1) the overall length has been increased by 3”, with the wide-point and the fin array both moved up from the tail that same distance. (2) The single, open tail concave has been replaced by dual open concaves, one on each side of the centerline, (3) there is now a small amount of “V” exiting the tail, (4) there is now a shallow single concave in the mid-third, between the entry and the exit contours, and (5) the shallow deck concave has returned. In an effort to maintain the same board-volume-to-rider-bodyweight ratio, I reduced both the thickness and the width. Thickness is now about 2" and width is 22-1/4". Volume is 23L.

Feedback from riders of the TBG3 as well as my own experience in riding the G3, suggested that a slightly longer outline (relative to rider length) might help to lessen the drag introduced by the rider’s thighs and knees. The longer length places the tailblock closer to mid-thigh when riding in the maximum planing efficient position. The extra length necessitated the movement of the wide-point/hip and adjacent fins to a point further forward. I place the wide-point and fins in the location close to the rider’s hip, where it serves as a pivot point for turning.

The exit single-concave concept was abandoned in favor of a dual-concave design. There were a couple of reasons for this. It is apparent to me, that when riding a wave prone (as opposed to paddling prone on a flat surface) the rear corner of the board closest to the wave face is the area of the bottom most in contact with the water. An open concave in this area serves to manage water flow, and increases “bite” at the rail by altering the rail profile. The single-concave in the middle of the bottom also provides lift in much the same manner, but is most effective when the rider’s weight is forward. Lastly, the performance gained by the hard-edged single concave did not justify the labor required to shape it.

The V added to the tail simply facilitates turning by making rail-to-rail transitions quicker. V also increases the rocker curve out at the rail. The end result of adding V is that the rocker along the stringer or centerline remains flat (for speed), while rocker at the rail increases (for turning on rail).

I eliminated the shallow deck concave on the TBG3, replacing it with a flat deck but found that when doing abrupt turns at speed I would sometimes slide off the deck in the opposite direction. During a turn in more powerful waves, the beach-side fins engage with authority, yielding an immediate change of direction. At such times, the centrifugal force is strong enough to pull my body off center. I’m hoping that the concave will help to keep me centered.

I plan to begin trials with my now standard quad fin set-up: Front Fins - True Ames Side Bites 3.7”, Rear Fins – TA SB 3.25”. Anybody in the Ventura-SB-LA area is welcome to sign up for a demo ride. I would appreciate the feedback.
Attachments
TBG4x_deck1.JPG
TBG4x_deck1.JPG (63.19 KiB) Viewed 2551 times
TBG4x_bot1.JPG
TBG4x_bot1.JPG (69.98 KiB) Viewed 2551 times
TBG4x_foil.JPG
TBG4x_foil.JPG (81.2 KiB) Viewed 2551 times
TBG4x_midconcave.JPG
TBG4x_midconcave.JPG (90.95 KiB) Viewed 2551 times
TBG4x_tailconcaves1.JPG
TBG4x_tailconcaves1.JPG (97.24 KiB) Viewed 2551 times
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Re: T-Belly Gen 4x

Unread postby soulglider » Thu Mar 12, 2015 11:01 am

cleanest version yet. looks like a lotta fin? wutta the rails look like?
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Re: T-Belly Gen 4x

Unread postby nomastomas » Thu Mar 12, 2015 1:51 pm

Thanks, SG, I would agree. I use the same rail shape as G2-3, which is primarily a sloped, tucked-edge rail, progressing quickly from an up-rail shape in the nose to a down-rail shape in the tail. As can be seen, I've tried to keep the outer 2" of the rail as thin as possible. I believe that a pinched rail offers superior wave penetration, providing excellent hold, which is then converted into forward speed. The tucked edge offers a release point for water flow, preventing drag from water wrap. (Water is actually very sticky stuff, and once it attaches to a surface, it doesn't want to let go. Edges encourage water to let go.) The foil and toe-in of the fins creates lift in the direction of the wave face (not in the direction of the deck), pulling the rail into the wave. This helps to keep the rail engaged.

I've done extensive testing with different fin configs and I've found this set-up to work best for a light-heavyweight rider (yours truly) in chest-high or better conditions. There are trade-offs in all surfcraft design, and of course fins are no exceptions. Fins create drag, plain and simple. But, if their use allows the rider to capture more speed, and/or better control, then that drag is an acceptable trade-off. I know from experience that the fin area of these fins fails to earn its keep when wave size drops below 3.5ft, and I down-size fin area accordingly, either by using smaller fins front and rear (in quad set-up) or removing the rear fins altogether and converting to a twin-fin set-up. That's the advantage of having removable fin boxes.
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Front view
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TBG4x_rails2.JPG
Rear view
TBG4x_rails2.JPG (74.18 KiB) Viewed 2538 times
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Re: T-Belly Gen 4x

Unread postby krusher74 » Thu Mar 12, 2015 3:07 pm

The evolution continues! :D

With the deck concave do you find you stay in the same place and just lean.

When I ride, my hip and elbow is on the edge of the rail, i'm only in the center of the board if i am going straight. (or middle of a cut back) I find I move around a lot. :?

I think I ride 23L also (found 25L to much) I am 5.10 170lbs

So this is EPS/epoxy again?
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Re: T-Belly Gen 4x

Unread postby nomastomas » Thu Mar 12, 2015 3:20 pm

Deck concave actually helps a lot, but doesn't eliminate all movement. I'm trying to eliminate the "half-on-half-off" predicament.

Everyone should get to know their preferred volume. There's really no right or wrong here, just what works for you. Thanks to CNC, I can dial in volume for each rider, while maintaining the integrity of the shape.

EPS/Epoxy..."the only way to fly!" (you youngster may not recognize the reference to the old Western Airlines motto) Double 4oz E-cloth deck/single 4oz E-cloth bottom.
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Re: T-Belly Gen 4x

Unread postby krusher74 » Thu Mar 12, 2015 5:37 pm

nomastomas wrote:Deck concave actually helps a lot, but doesn't eliminate all movement. I'm trying to eliminate the "half-on-half-off" predicament.

Everyone should get to know their preferred volume. There's really no right or wrong here, just what works for you. Thanks to CNC, I can dial in volume for each rider, while maintaining the integrity of the shape.

EPS/Epoxy..."the only way to fly!" (you youngster may not recognize the reference to the old Western Airlines motto) Double 4oz E-cloth deck/single 4oz E-cloth bottom.



Heard and used the same quote, but had no idea of its origin :oops:

I was recently looking at marko EPS recycled foan and supersap eco resin, that would be towards a eco board.

I did not get onn with my first EPS board, but i think it not enough dencity on the EPS and to much glass and epoxy giving that pop out feel. Hopefully I will get to try one of yours someday.. :D
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Re: T-Belly Gen 4x

Unread postby ClanB » Sat Mar 14, 2015 9:03 pm

T-Belly has come a long way...and it started out pretty good in the 1st place. The rails look like they would stick to a steep wall well.
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Re: T-Belly Gen 4x

Unread postby Daryl D » Sun Mar 15, 2015 8:02 pm

Nice board Thomas. I've really enjoyed the G2 I have, but I think the changes you've made are all good. I think you're right on about the length. I also like the channels. Let me know when you're ready to sell it. I know I out weigh you 30 lbs, but after riding wood paipos, buoyancy is relative.
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Re: T-Belly Gen 4x

Unread postby nomastomas » Mon Mar 16, 2015 4:37 pm

ClanB - yes, that's the idea. I'm in Tucson until next week, so I haven't been able to take it for test ride yet. Looks like we have some waves coming next weekend, so...

Daryl - Yes, buoyancy is relative. Everyone has a different comfort zone. I don't foresee any major design changes over the next year, so this one is a keeper. I'm a little concerned about the the extra 3" of length, and how it will impact my paddling position. I've got another solution to this problem in mind.
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Re: T-Belly Gen 4x

Unread postby bgreen » Tue Mar 17, 2015 6:03 am

Thomas,

If you'd like the interview updated let me know. Just send photos and text and we can go from there.

Bob
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